Implement sequential focus navigation for OOPIF.

third_party/WebKit/Source/core/page/FocusController.cpp

Index: third_party/WebKit/Source/core/page/FocusController.cpp
diff --git a/third_party/WebKit/Source/core/page/FocusController.cpp b/third_party/WebKit/Source/core/page/FocusController.cpp
index 4bde2a973602ff3a8b47548ee964adbf8b974499..d0a97c766d642b7b795dde89cc6186e43e788ff7 100644
--- a/third_party/WebKit/Source/core/page/FocusController.cpp
+++ b/third_party/WebKit/Source/core/page/FocusController.cpp
@@ -43,6 +43,7 @@
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
+#include "core/frame/RemoteFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLAreaElement.h"
 #include "core/html/HTMLImageElement.h"
@@ -690,8 +691,13 @@ bool FocusController::advanceFocus(WebFocusType type, bool initialFocus, InputDe
 {
     switch (type) {
     case WebFocusTypeForward:
-    case WebFocusTypeBackward:
-        return advanceFocusInDocumentOrder(type, initialFocus, sourceCapabilities);
+    case WebFocusTypeBackward: {
+        // We should never hit this when a RemoteFrame is focused, since the key
+        // event that initiated focus advancement should've been routed to that
+        // frame's process from the beginning.
+        LocalFrame* startingFrame = toLocalFrame(focusedOrMainFrame());
+        return advanceFocusInDocumentOrder(startingFrame, nullptr, type, initialFocus, sourceCapabilities);
+    }
     case WebFocusTypeLeft:
     case WebFocusTypeRight:
     case WebFocusTypeUp:
@@ -704,17 +710,30 @@ bool FocusController::advanceFocus(WebFocusType type, bool initialFocus, InputDe
     return false;
 }
 
-bool FocusController::advanceFocusInDocumentOrder(WebFocusType type, bool initialFocus, InputDeviceCapabilities* sourceCapabilities)
+bool FocusController::advanceFocusAcrossFrames(WebFocusType type, RemoteFrame* from, LocalFrame* to, InputDeviceCapabilities* sourceCapabilities)
+{
+    // If we are shifting focus from a child frame to its parent, the
+    // child frame has no more focusable elements, and we should continue
+    // looking for focusable elements in the parent, starting from the <iframe>
+    // element of the child frame.
+    Node* startingNode = nullptr;
+    if (from->tree().parent() == to) {
+        ASSERT(from->owner()->isLocal());
+        startingNode = toHTMLFrameOwnerElement(from->owner());
+    }
+
+    return advanceFocusInDocumentOrder(to, startingNode, type, false, sourceCapabilities);
+}
+
+bool FocusController::advanceFocusInDocumentOrder(LocalFrame* frame, Node* startingNode, WebFocusType type, bool initialFocus, InputDeviceCapabilities* sourceCapabilities)
 {
-    // FIXME: Focus advancement won't work with externally rendered frames until after
-    // inter-frame focus control is moved out of Blink.
-    if (!focusedOrMainFrame()->isLocalFrame())
-        return false;
-    LocalFrame* frame = toLocalFrame(focusedOrMainFrame());
     ASSERT(frame);
     Document* document = frame->document();
 
-    Node* currentNode = document->focusedElement();
+    Node* currentNode = startingNode;
+    if (!currentNode)
+        currentNode = document->focusedElement();
+
     // FIXME: Not quite correct when it comes to focus transitions leaving/entering the WebView itself
     bool caretBrowsing = frame->settings() && frame->settings()->caretBrowsingEnabled();
 
@@ -726,6 +745,14 @@ bool FocusController::advanceFocusInDocumentOrder(WebFocusType type, bool initia
     RefPtrWillBeRawPtr<Element> element = findFocusableElementAcrossFocusScopes(type, FocusNavigationScope::focusNavigationScopeOf(currentNode ? *currentNode : *document), currentNode);
 
     if (!element) {
+        // If there's a RemoteFrame on the ancestor chain, we need to continue
+        // searching for focusable elements there.
+        if (frame->localFrameRoot() != frame->tree().top()) {
+            document->clearFocusedElement();
+            toRemoteFrame(frame->localFrameRoot()->tree().parent())->advanceFocus(type, frame->localFrameRoot());
+            return true;
+        }
+
         // We didn't find an element to focus, so we should try to pass focus to Chrome.
         if (!initialFocus && m_page->chromeClient().canTakeFocus(type)) {
             document->clearFocusedElement();
@@ -760,6 +787,14 @@ bool FocusController::advanceFocusInDocumentOrder(WebFocusType type, bool initia
 
         document->clearFocusedElement();
         setFocusedFrame(owner->contentFrame());
+
+        // If contentFrame is remote, continue the search for focusable
+        // elements in that frame's process.
+        // clearFocusedElement() fires events that might detach the
+        // contentFrame, hence the need to null-check it again.
+        if (owner->contentFrame() && owner->contentFrame()->isRemoteFrame())
+            toRemoteFrame(owner->contentFrame())->advanceFocus(type, frame);
+
         return true;
     }